...you're comparing a 10 man BH (where shadow priests dominate due to aoe) to a 25 man Baelroc (where you're probably assigned to soaking a crystal, thus not attacking for 6s and potentially letting dots drop). Your actual dps numbers are irrelevant since the fights are so different. As for the DI uptime/actual benefit gained, I think you're either just misunderstanding how the buff works or the warlock in the 25 man was just absolutely terrible.

Actually, WoL will tell you how much of each activity is being done.
Just Log the fight with /combatlog (or /combatlogs I can never remember) and get the WoWConbatLog.txt out of the logs directory and upload it to WoL.

I'm sorry guys, maybe the warlock dies alot, maybe he cancels di mid fight, idk but like, I KNOW when I get 3 stacks, like I just do crazy dps, and my guild is complaining to me that I am not doing as much dps with all my gear and I honestly think this is why. If I can do 27k in 10 man BH with just reg buffs and DI and a hero, I should be doing 30k+ with the same buffs, and I see this on the logs for other shadow priests.

I'm prob just losing my mind but it really bugs me now because It's so obvious when I get 3 stacks of DI as my dps increases exponentially lol. But I don't know, if I did, i really wouldn't be posting would I?

Keep in mind even if it was up 100%, that's only a 3% (1% per stack) bonus to your dots, so chances are even if you get it figured out and raise your uptime that won't be enough to satisfy your guild since the difference will be trivial, basically a rounding error. Not that I'm being critical, just trying to put some perspective on your guild dilemma.